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Understanding the Method

Addition problems can sometimes seem daunting, especially with larger numbers. The trick to making them more manageable is to group numbers into round figures—multiples of ten or a hundred. Let's break down this method using some examples.

Example 1: 63 + 427

1. Initial Setup: We start with the problem 63 + 427. It looks complex, but we can simplify it by adjusting these numbers to round figures.

2. Rounding the Numbers: To make 63 a round number, we need to subtract 3 (making it 60). If we add those 3 to 427, it becomes 430.

3. Simplified Calculation: Now, the problem transforms into 60 + 430. This is much easier to handle and can be calculated mentally to get 490.

Example 2: 275 + 595

1. Breaking It Down: Here, we start with 275 + 595. To simplify, we break 275 into 270 + 5.

2. Adjusting and Rounding: We then add the 5 to 595, making it 600. The new problem is 270 + 600.

3. Easy Addition: This simplifies the calculation to a straightforward mental math problem, resulting in 870.

Example 3: 51 + 83

1. Initial Problem: We start with 51 + 83. By increasing 83 by 1 to make it 84, we need to decrease 51 by 1, resulting in 50.

2. Simplified Addition: This changes the problem to 50 + 84, which is easier to compute as 134.

Example 4: 138 + 710

1. Adjusting Numbers: Starting with 138 + 710, we subtract 10 from 710 (making it 700) and add that 10 to 138 (making it 148).

2. Final Calculation: The problem simplifies to 148 + 700, resulting in an easy mental calculation of 848.

Key Concept:

By adjusting one number up and the other down by the same amount, we simplify the problem without changing the overall value.